Regardless of whether Nickle to Copper fusion can occur in the conditions that Rossi claims for the Ecat, the input and output of "fuel" isn't in line with what would happen.
That is, given what his input Nickel fuel is, the output "spent" fuel after the run would look radically different than what Rossi has shown.
In fact, his "spent fuel" looks very much like: he went out and put together a fuel rod from commerically-available Nickel and Copper, and didn't bother to do the actual Physics behind what the Isotope ratio should be, then just pulled this "fuel rod" out of the device to "prove" it worked.
Also, as pointed out by the article, if his Ecat worked as he claims, everyone would be dead within 10 minutes of starting the reactor, due to massive Gamma radiation leaks.
One can claim that low-temperature fusion is happening, for some reason we don't understand. But then you can't go on and claim that the actual fusion process is somehow different than all possible combinations using your input and output elements.
Since Rossi's still alive to peddle his snake oil, it's plainly, well, snake oil.